Sequence stratigraphic expression of greenhouse, transitional and icehouse conditions in siliciclastic successions: Paleozoic examples from the central appalachian basin, USA

• Published in: Earth-science reviews 2019-01, Vol.188, p.176-189
• Main Authors: Eriksson, Kenneth A., McClung, Wilson S., Simpson, Edward L.
• Format: Article
• Language: English
• ISSN: 0012-8252; 1872-6828
• DOI: 10.1016/j.earscirev.2018.11.010

Climates during the Paleozoic varied from greenhouse to transitional to icehouse and siliciclastic successions deposited during those times have stratigraphic architectures consistent with magnitudes and frequencies of sea-level fluctuations at the time of deposition. Three Central Appalachian Basin Paleozoic successions, the Early Cambrian Chilhowee Group, the Late Devonian Foreknobs Formation, and the Early Pennsylvanian Breathitt Group, are compared and contrasted to develop models that relate stratigraphic architectures to greenhouse, transitional and icehouse conditions existing on Earth. Within the upper portion of the Early Cambrian Chilhowee Group, the Hampton and Erwin Formations represent a succession of 2 Myr (3rd-order) sequences consisting of stacked, 40–80 kyr (5th-order), marine parasequences that record low-magnitude, high-frequency sea-level changes consistent with greenhouse conditions. The Late Devonian Foreknobs Formation consists of a series of 0.8–1.0 Myr (3rd-order) composite sequences comprised of stacked unconformity-bounded, 225 to 450 kyr (4th-order) sequences, each containing 40 to 65 kyr (5th-order), marine parasequences. The bases of the unconformity-bounded sequences are marked by erosional surfaces (regressive surfaces of marine erosion, fluvial deposits, or paleosols) indicative of sea-level drops of 10 to 45 m consistent with a transitional greenhouse to icehouse climate. The Early Pennsylvanian Breathitt Group consists of stacked, unconformity-bounded, 100 kyr (4th-order) sequences that lack parasequences. Unconformity-bounded sequences are comprised of (from bottom to top): lowstand incised valley, braided alluvial deposits; transgressive tidal estuarine deposits; and progradational, highstand deltaic deposits. Depths of incised valleys and vertical transition into estuarine facies imply sea-level changes of >50 m consistent with icehouse conditions. This study demonstrates that siliciclastic successions preserve a record of sea-level changes consistent with greenhouse, transitional, and icehouse conditions on the Paleozoic Earth.